Various types of circuits and systems use oscillators in order to generate clock signals or other types of signals. In some oscillator designs, the oscillator frequency is determined by a Resistor-Capacitor (RC) network. In some Integrated Circuit (IC) configurations, the oscillator is contained within the IC but the frequency determining RC network is external to the IC. In these configurations, the external RC network is connected to the IC via one or more input pins. Some RC oscillator configurations use only a single pin for connecting to the IC, and are therefore referred to as single-pin configurations.
For example, U.S. Pat. No. 4,122,413, whose disclosure is incorporated herein by reference, describes a single-pin Metal Oxide Semiconductor (MOS) RC oscillator in which a series resistor-capacitor combination is coupled across a source of supply potential so that the capacitor charges toward the supply potential through the resistor. The capacitor is discharged through a shunt-connected switch that is operated by means of a latch. Two inverters, which are coupled to the capacitor, respond to the capacitor charge and operate through logic means to set and reset the latch. The inverters have similar but different thresholds. When the capacitor charge is below both thresholds, the latch is set to turn the switch off so that the capacitor charges. When both thresholds are exceeded, the logic resets the latch to turn the switch on and discharge the capacitor.